Spray gun



Dec. 2, 1952 F. scHuMAcHER SPRAY GUN Filed Dec. 2, 1949 Rlv w RR w ANM. M mm w a M W Vm 1m A w Patented Dec. 2, 1952 NH'FED S'i'ATES PTENT FFICE Claims.

This invention relates to spray guns, more particularly spray guns for materials which melt at a comparatively low temperature, and especially for low melting point metals.

The primary object of the present invention is to generalfy improve spray guns of the specified character. A more particular object is to improve eiciency by providing means for heating the material the gun from the inside, that is, the material to be heated surrounds the heating element.

The flow of the molten material is Controlled by a Valve which extends through the material. In accordance With a further feature and object of the present invention the Valve stem is made hollow and of substantial diameter, and the heating element is protectively housed within the hollow valve stem. This has the added advantage of insuring the application of heat to the material at the discharge opening where it is most important to insure liquidity.

A further object of the invention is to accurately control the temperature to which the molten material is heated. For this purpose the spray gun is provided with a thermostat which controls the energization of the heating unit. In accordance with one object of the present invention the thermostat is located on the outside of the cup or Chamber carrying the molten material, and this in turn insures flow of heat through the material surrounding the heating unit.

For most spray purposes an extensive area is to be coated, and a diifused spray is desired. However, this causes difculty when it is sought to localize the spray or coating of material to a Very small area, as, for example, in a corner between angularly related walls. It is accordingly an object of the present invention to facilitate localized coating as well as extensive coating, and for this purpose I provide an annular air discharge opening which is frusto-conical in shape. The frustoconical walls are made substantial in axial dimension in order to guide the air flow toward a focal point. If then the gun is held at approximately the focal distance a concentrated spray is obtained by means of which a small area may be coated, but if the gun is held at a substantially greater distance a diifuse spray is obtained by means of which an extensive area may be coated.

In accordance with another feature and object of the invention the ratio of air to molten material may be adjusted, and for this purpose the outer wall of the annular air passage is made separate from the inner wall, with 'a yieldable gasket disposed between the parts Where they join. A threaded adjusting ring is provided for adjusting the pressure on the gasket and thereby slightly moving the outer wall in axial direction relative to the inner wall. Because of the frustoconical shape of the parts this changes the width of the annular air passage between the walls, and thus changes the air-to-metal ratio.

To accomplish the foregoing objects, and other more detailed objects which will hereinafter appear, my invention resides in the spray gun elements and their relation one to another, as are hereinafter more particularly described in the following specification. The specification is accompanied by a drawing in which:

Fig. 1 is a, section taken in elevation through a spray gun embodying features of my invention;

Fig. 2 is a side elevation looking toward the end of the handle;

Fig. 3 is a transverse section taken in the plane of the line 3-3 of Fig. 1;

Fig. 4 is a section similar to Fig. l but localized to the air valve, and drawn to enlarged scale;

Fig. 5 is 'a fragmentary section similar to Fig. l, but localized at the nozzle, and drawn to enlarged scale; and

Fig. 6 is a plan view.

Eeferring to the drawing, and more particularly to Fig. 1, the spray gun comprises a cup |2 for a supply of the material lt, which is solid at room temperature but which may be melted in the cup 12. The gun has a nozzle portion generally designated N, the said nozzle portion having a material discharge opening IG, and an air discharge opening i8 for atomizing the material passing through opening IB. The gun furthei' comprises a heating unit 2B disposed in the middle of cup l2 to heat the surrounding material 14.

The fiow of molten material is controlled by a suitable Valve 22, and the fiow of air, received throughV a nipple 24, is Controlled by a suitable valve 25. These valves are preferably both controlled by a single control lever 23. As here illustrated the lever is moved toward the handle 30, that is, from the solid line position 28 to the broken line position 28', to open the valves and thus begin the spraying operation.

Considering the arrangement in greater detail, the cup |2 is made of a heat-resistant and corrosion-proof material, 'preferably stainless steel. In the present case the cup is made of a piece of open-ended stainless steel tubing which is closed -at the bottom by a machined part 32. The parts are secured together in any desired fashion, -here illustrated by a threaded connecaaopae 3 tion at 32. The part 32 is projected downwardly to provide a valve seat portion 36 and a n-ozzle portion 38. The valve seat portion 35 is :conically shaped, and is ground to accurately fit the cone-shaped valve 22. These, like the other parts constant'ly exposed to the molten metal in the cup, are preferably made of stainless steel.

The valve tip 22 is carried by a tubular valve stem iii) which is also made of stainless steel. This receives a suitable electrical resistance heating unit 2B, for example a commercially known Calrod unit, of such dimension as to substantially fill the valve Stern. The -lower portion of the valve stem is `slidably guided in a suitable bearing or ring fiiZ, centrally located in the cup by means of a pair of radial arms 54 which extend outwardly to the cup wa'll. This :bearing is also made of stainless steel. The upper end of the valve stem is slidably received in and guided by a bearing li. This is not immersed in 'the molten metal iii and may be made of a light-weight metal such |as aluminum. It may lbe formed 'as part of a die casting, another part 138 of which acts as a protective hous'ing for the electrical conductors 513 leading to the heating unit 2il. The valve is normally u'rged downward to closed position by means of a compression spring 52 housed within the upper guide portion 4%. The conductors 59 pass through the compression spring 52 as shown.

Referring now to F-ig. 4 of the drawing, air is supplied through a suitable fiexible -air hose indicated at 54, the end of which is slid over a conventional nipple 24. The nipple has a threaded 'end 56 screwed into a suitable boss 58 on an outside housing 6B. The h'ousing 6G is preferably made of a die-cast light-weight metal such as ailuminum, and serves a number of different purposes explained later. One of these is to carry the air valve mechanism next described.

The air valve is a frusto-conically shaped Valve indicated at 62. It is shown in open position in Fig. 4, and in closed position in Fig. l. It is normally urged upward to closed position by a compression spring 55. It is guided by an upwardly drected valve stem portion 56 slidable in a bearing 68. This may be formed directly in the aluminum housing member BE), but is preferably made a 'separate sleeve of harder metal as shown. Similarly, the valve seat indicated 'at l might be formed directly in the 'aluminum housing but is preferably made a separate bushing so that a more durable metal may be employed. The pieces 68 and w are secured in position in any desired fashion, as by means of a force fit or a screw thread, etc. The portion of the valve stem E within the guide bearing E8 is preferably grooved with a plurality of spaced annular grooves indicated at 12, thus forming a seal against leakage of |air upwardly around the valve stem. When the valve is moved downwardly to open the same, air fiows down around the valve and through a connection or 'a coupling -indicated at Tlfil to a piece of tubing lt, which may be made of copper.

Referring now to Fig. 1 of the drawing, the tube 16 is connected lby means of a coupling 78 to the nozzle portion N of the gun. More specically, the connection leads into an outer part 89 of the nozzle. Referring now to Fig. 5, the inner and outer parts are spaced to form an V'annular air space 82 of substantial cross-seeti-on therebetween, and the connection T8 leads into said air space, which then acts as a means to distribute the 'air entirely 'around the nozzle. Inasmuch as this part of the gun is heated by the molten metal, the `annular space S2 serves the additional purpose of preheating the air somewhat -before it comes into contact with the molten material.

The outer part S' is suitably connected to the gun, and is preferably arranged for 'a slight axial movement. In the present case the upper rim is fianged outward at 813, and a yieldable gasket 83 is disposed above the flange 8:3. A suitable clamping ring 88 has an inwardly directed fiange 9G which bears against the fiang'e 84. The clamping ring 88 is internally threaded and is preferably provided with fiats on the outside, as is .best shown in Fig. 2, thus facilitating rotational adjustment of the ring. The gasket 8 is preferably made of a heat-resistant material such as .asbestos It will be evident that the gasket serves a primary purpose in preventing leakage of air. It serves an additional purpose in making it possible to slightly adjust the axial position of the outer member 88 of the nozzle, relative to the inner part 38. Because of the frusto-conical shape of the air discharge vpassage IS, such axial 'adjustment varies the width or thickness lof the passage.

Upward movement narrows the passage, and downward movement Widens it. This varies the ratio of air to molten metal for any given fixed adjustment of the valves, and Aso dispenses with the need for `adjustable valves.

The conicity or taper of the air passage 18 has been exaggerated in the drawing for the sake of clarity. It will be understood that in practice the taper may be quite small. In one practical construction of the present spray gun the taper is made such as to bring the air flow to a focus at a distance of approximately 4 from the nozzle. Thus by bringing the gun close to the work the coating may be localized to a small area, and one may suocessfully spray into corners. However, by spacing the gun a more normal distance from the object being coated, Say 12" or more, the spray is diffused, and a coating may be applied over a fairly large area.

The valves 22 and 25 are Controlled by the lever 28 in the following manner. A vertically movable slide 92 is slidably carried and guided within the housing 6G previously referred to. The inner face of the slide 92 may bear against the outer wall of the tubular cup IZ, thus simplifying the assembly, for it is merely necessary to place the slide 92 in an open slot in housing 6G before fastening the housing to the outside of the cup. The slide 92 is notched near its lower end, as indicated at 94 (Fig. 4) to receive the forward end 96 of lever 28, the latter being pivoted at 93. It will be evident that when control lever 28 is raised the slide 92 is lowered.

The lower end of the slide is projected outwardly to overlie the stem E5 of the air valve, as is indicated at lfil. There is preferably little or no lost motion at this point, and downward movement of the slide consequently causes immediate opening of the air Valve.

Referring now to Fig. 1, the upper end of slide 92 is preferably inwardly notched, as is indicated at U32. Notch m2 receives the outer end of a lever llfil which is pivoted at l, and the inner end m8 of which is bifurcated to straddle the Valve stem 43, as is best shown in Fig. 3. Suitable pivots, in this case a pair of short screws lit, act as trunnions to connect the lever to the valve stem. It will be evident that downward moveznent of the slide .92 causes a clockwise rotation of the lever and consequently an upward movement of the valve stem do. It should be noted, however, that the notch M32 is made long enough to provide appreciable lost motion before the valve stem "59 is raised. This insures opening of the air valve before any of the r'iolten material is permitted to iow through the passage E5. There accordingly no danger of flow of molten material which has not been atomized.

IThe temperature to which the melt-en material is heated is preferably automatically Controlled, as by means of a thermostat indicated at iii. This therrnostat is preferably housed in the housing od previously rcferred to. Here again the housing preferably open on the inside, it being closed by the stainless steel cup [2 against which the housing and thermostat are secured. Thus i the therinostat is responsive to the temperature of the and the assembly of the parts is facilitated, it being necessary to merely place the thermostat in the housing before seouring the housing to the cup. The thermostat controls the heating of the material in any desired inanner, the simplest and most common method being the pro-vision of an on-and-off switch Controlled by and forming a part of the thermostat assembly, the said switch eirr7 connected in the circuit leading to the heater unit Eli. Such arrangements are too simple and too well known to require a special wiring diagram, but it will be seen in Fig. 1 that the iiexible power supply cord l Ill is connected at a protected point lli within the housing to to both the thermostat unit M2 and the heater unit The power supply cord Hfi is made of convenient length, and terminates in a conventional plug which may be plugged into a mating power outlet, such as an ordinary 1143 Volt wall outlet.

The temperature maintained by the thermostat is preforably made adjustable, and in the present case the adjustment is made by means of an externally accessible screw indicated at llf in Fig. 2. The particular gun here shown is intended for use with low melting point metals or a-lloys such, for example, as those made by Cerro de Pasco Copper Corporation, which include Cerrobend, having a nielting point of l58 l; Cerrobase, having melting point of 255 and numerous other alloys having inelting points ranging all the wav from 117 F. to 540 F. In the present gun the thermostat is preferably one which may be adjusted over that entiro range.

'from inspection of Figs. and 5 of the e, the aluminum piece do, 4. previously referred to preferably includes in ad-n dition a pair of outwardly projectine arms i which are iitted within the top edge of the cup E2, and which serve to prcperly locate the bearing Lit for the upper end of the valve stem. ends of the arrns iii are preferably projected upvvard to form ears E22 which receive the inturned ends of a suitable bail i'i. The bail is broken away in Figs. l and 2, but is better shown in Figs. 3 and 6 of the drawing. A suitable chain and hook (not shown) be suspended from the ceiling or other support, and used to hold the spray either when not in use, 01' during use to reduce the fatigue of the operator. The gun may be manipulated by means of the main handle 39, even though it is suspended from above by means of the bail 121i. If desired the support chain may be run over a pulley and provided with a counterweight, thus making it readily possible to raise Or lower the gun while using the same.

Referring to Figs. 1 and 6, it will be seen that the handle 30 is secured to a suitable boss |2i5 forming a part of the aluminum housing 60 previously referred to. The handle may be made of Wood or Bakelite or other suitable material, and is secured to the post l26 as by means of a long screw 128. In Fig. 6 it will be seen that the aluminum housing 60 is fitted edge-to-edge at |30 to the aluminum part 48 previously referred to, and in Fig. 2 it will. be seen that the resulting assembly is secured to the outside of the cup l2, as by means of screws |32. In Fig. 3 it will be seen that the assembly is additionally held by diametrically opposed screws |34. These help take the load of the gun when suspended by the bail 124.

It is believed that the method of constructing and using my improved spray gun, as well as 'the advantages thereof, will be apparent from the foregoing detailed description. It will also be apparent that while I have shown my invention in a preferred form, changes may be made in the structure shown without departing from the scope of the invention as sought to be defined in the following claims.

I claim:

l. A spray gun for a low melting point metal which is solid at room temperature, said gun comprising a stainless steel cup for a supply of the metal, and a nozzle portion at the bottom of the cup, said nozzle portion having a metal discharge opening and an air discharge opening for atomizing the molten metal, a valve for the metal, a valve for the air supply, a single control lever for Operating both valves, a heating unit protectively housed in a stainless steel tube having a closed bottom and disposed downwardly from above in the middle of the cup to heat the immediately surrounding low melting point metal in the cup in order to melt the same, and means connecting a cold air supply to the nozzle at a point below the heater.

2. A spray gun for material which is solid at room temperature, said gun comprising a cup for a supply of the material, said gun having a nozzle portion With a material discharge opening, a Valve and hollow valve stem in said cup for controlling the flow of material through said opening. said nozzle portion having an air discharge opening for atomizing the material, a valve for the air supply, a single control lever for operating both valves, and an electrical resistance heating unit disposed in the hollow valve stem in order to heat the surrounding material in the cup.

3. A spray gun for material which is solid at room temperature, said gun comprising a cup for a supply of the material, a nozzle portion at the bottom of the cup, said nozzle portion having a material discharge opening, a valve and hollow valve stem extending upwardly through the middle of the cup for controlling the flow of material through said opening, said hollow portion of said valve stem being closed at the bottom, said nozzle portion having an air discharge opening for atomizing the material, a valve for the air supply, a single control lever for Operating both valves, and an electrical resistance heating unit disposed in the hollow valve stem in order to heat the surrounding material in the cup.

4. A spray gun for a low melting point metal which is solid at room temperature, said gun comprising a stainless steel cup for a supply of opening, said hollow portion of said valve' stem being closed at the bottom,,said nozzle portion having an air discharge opening for atomizing the molten metal, a valve for the air supply,`a single control lever for operating'both valves, and an electrical resistance heating unit disposed in the hollow valve stem in order to heat the surrounding low melting point metal in the cup.

5. A spray gun for loW-melting point materials which are solid at room temperature, said gun comprising a cup for a supply'of the material, a nozzle portion at the bottom of the cup, vsaid nozzle portion having a material dischargeopening, a hollow valve stem 'for controlling the flow of material, an electrical heating'unit disposed z within the hollow valve stem for heating the surrounding material in the cup, said nozzle portion having an annular air discharge opening surrounding the aforesaid material discharge opening, an annular passage disposed above and communicating with said annular discharge opening, an air supply line leading to said annular passage, said annular opening being frustroconical in shape, the outer wall being separate from the inner wall and connected to the bottom of the spray gun with a yieldable heat resistant gasket disposed therebetween, and a threaded adjusting ring for adjusting the pressure against the gasket and thereby moving the outer wall axially relative to the inner wall and thereby changing the width of the annular space between the parts in order to adjust the ratio of air to material, said annular frustro-conicalwalls being substantial in axial dimension in order to guide the air flow to a focal point to facilitate coating in a corner. h

6. A spray gun for material which is solid at room temperature, said gun comprising a Vcup for a supply of the material, said gun having a nozzle portion with a material discharge opening and an air discharge openingforatomizing the material, an electrical'heating'unit disposed in the middle of the cupA to heat the surrounding material in the cup, and a thermostat toflcontrol the operation of said heating unit, said thermofstat being located at and being responsive to the temperature at the outside of thecup.: i z

1'7. A spray gun formaterial which is -usolid at room temperature, said gun comprising a cup for a supply of the material, said gunA having a nozzle portion with a material discharge opening, a valve and hollow valve stem in saidcupfor controlling the flow of material through said-opening, said nozzle portion'having an air-discharge opening for atomizing the material, a valve for the air supply, a single control lever for Operating both valves, an electrical heating unit disposed inside'the hollow valve stem to heat thersurrounding material in the cup, and a thermostat to control the operation of said heating unit, said thermostat being located at and Vbeingrresponsive to the temperature at the .outsideof thecup. o

8. A spray gun for material which issolid at room temperature, said gun comprising VVacup for a supply of the material, a nozzle portion at the bottom of the cup, said nozzle portion having amaterial discharge Opening, 1a' valve and hollow valve stem extending upwardly through the middle of the cup for controlling the flow of material through said opening, the upper end of said valve stem being slidably received in a guide secured at the top of the cup by a lateral support, said nozzle portion having an air discharge opening for atomizing the material, a valve for the air supply, a single control lever for Operating both valves, the linkage between said lever and said valve stem being carried around the top of the cup to a point on the valve stem below the guide, and an electrical heating unit disposed in the hollow valve stem in order to heat the surrounding material in the cup, the conductors for supplying power to said heating unit passing upward through the guide and laterally through the support of the guide.

9. A spray gun for material which is solid at room temperature, said gun comprising a cup for a supply of the material, a nozzle portion at the bottom of the cup, said nozzle portion having a conical valve seat and a material discharge opening, a valve and hollow valve stem extending upwardly through the middle of the cup for controlling the flow of material through said opening, said hollow portion of said valve stem being closed at the bottom, and having a conical lower end cooperating with said conical valve seat, said nozzle portion having an air discharge opening for atomizing the material, a valve for the air supply, a single control lever for Operating both valves, and an electrical heating unit disposed in the hollow valve stem in order to heat the surrounding material in the cup and at the valve seat.

10. A spray gun for material which is solid at room temperature, said gun comprising a cup for a supply of the material, a nozzle portion at the bottom of the cup, said nozzle portion having a conical valve seat and a material discharge opening, a valve and hollow Valve stem extending upwardly through the middle of the cup for controlling the flow of material through said opening, said hollow portion of said valve stem being closed at the bottom, and having a conical lower end cooperating with said conical valve seat, the upper end of said valve stem being slidably received in a guide secured at the top of the cup, said nozzle portion having an air discharge opening for atomizing the material, a valve for the air supply, a single control lever for Operating both valves, the linkage between said lever and said valve stem being carried around the top of the cup to a point on the valve stem below the guide, and an electrical heating unit disposed in the hollow valve stem in order to heat the surrounding material in the cup, the conductors for supplying power to said heating unit passing up- Ward through the guide and laterally through the support of the guide.

FRANZ SCHUMACHER.

REFERENCES CITED The' following references are of record in the z file of this patent:

UNITED STATES PATENTS 'iumber Name Date l,58'7,736 Schenck June 8, 1926 1,754,382 Baracate Apr. 15, 1980 2,058,971 Forton Oct. 27, 1936 2,252,942 Mourer Aug. 19, 1941 2,434,911 Denyssen Jan. 1, 1948 

